Bike Storage: Wall mounts, stands, lock-ups, sheds, etc.

If the hex heads are accessible under the putty, you might well be able to undo the bolts with a decent impact driver (definitely not a single Allen key or a combi drill) but the expanding sleeves are underground forever. You'd need to get a new set of the bolts. For the hassle and cost I'd probably leave it in unless you're obliged to remove it, and fit a new one in your next place.

Edit: just seen that those exact Squire ones are quite pricey! New set of bolts to reinstall it then. M10 expanding hex bolts should be what you need.